Grinding implement for articles of hard material



- March 19, 1946. RH, HOOD 2,397,005 I T FOR ARTICLES 0 ARD MATE Filed Sept. 21, 1945 haw/7dr Fe 5617/1. 170042,

Patentetl Mar. 19, 1946 GRINDING IMPLEMENT FOR ARTICLES OF HARD MATERIAL Reuben H. Hood, Durango, Colo.

Application September 21, 1945, Serial No. 617,751

3 Claims.

My invention-relates to a grinding implement or so called .cone-lap used in grinding, shaping and polishing hard-faced articles, such as stone, glass, diamonds and other gems as well as hard metal and porcelain, in other words, a lapi- ,dary tool.

This cone-lap which is preferably made of cast iron in one piece, has the form of a hollow cone or cup-shaped member, with a shank for securing it to a spinning shaft or arbor revolvable in both directions.

The preferred construction of this implement or cone-lap is illustrated in the accompanying drawing wherein:

Figure 1 is a top plan view of the implement, and

Figure 2 is an axial section along line 22 of Figure 1.

This tool, as already stated and as here shown is a one-piece, iron casting and has a narrow shank I adapted for securing by means of a set screw II on the end of a vertical shaft or arbor which is revolvable either in right hand or left hand direction.

Besides its shank I0 having the bore l9, the tool consists of a middle or tapered portion l2 and an outer or table portion I3 all made in one continuous casting with thick walls so as to resist breaking at high speed of rotation.

The walls of the tapered portion l2 of the tool merge on the outside at the smaller end with the shank l0 and then taper uniformly upwards as far as the abrupt shoulder l 4 with well-rounded corners forming the bottom part of the table portion or head l3. The top or head of the table portion l3 has a flat, horizontal surface 22 running at right angles to the axis of the tool.

The cavity of the tool consists of a depression l5 about one inch deep with a flat bottom l6 and inclined side surfaces II at an angle of about 18 against the vertical.

Coaxial with the depression l5 in the tool a central cavity I8 is formed in the shape of an inverted cone with its base in the bottom It of the depression l5 having a taper of about 36 and terminating short of the bore IS in the shank l0, but it does not connect therewith. The corners where the sides 20 of the cavity [8 merge with the bottom It are well rounded, but the corners at the top and bottom surfaces 22 and I6 of the depression l5 are preferably sharp.

Suitable dimensions for a tool of this character are about five and one-half inches overall length, about five and one-quarter inches, largest diameter of head [3, and one and one-half outside diameter of shank Ill, with walls 12 of uniform thickness about three-quarters of an inch.

The operation of this tool is the following: the article to be shaped, ground or polished is cemented to a rod or wooden handle (so-called lap stick). As cementing material wax may be used. This rod is held firmly in one hand, the cone-lap is then started to revolve with an abrasive covering the surfaces of its cavity and the stick with the article attached held in the cavity.

If the article is to have a circular shape, the article is then pushed down into the inner cav-' ity l8.

In order to grind the article to produce an oval, convex shape, the rod with the article is held tilted in the cone-lap and one side ground on one side against one side f the cavity l8 and the other side of the article ground on the opposite side of cavity [8.

To produce a concave grind the article is pressed against the rounded edge 20. In order to grind flat surfaces on objects with square,

rectangular, hexagonal and triangular shapes,

the same is pressed against the flat bottom 16 of depression l5.

Finally for grinding the crown of a gear the rod is held at an angle of about 20 with the face of the gear against the side surface I! of the depression [5.

Many designs and shapes may be obtained by combining the here enumerated methods. All gems and stones ground on this cone-lap have the proper basic angles.

By the use of the same all grinding is speeded up, more accurate Work obtained and less power required than with any now known methods and implements.

It i to be understood that many changes may be made in details and shape as Well as material within the scope of the subjoined claims.

I claim:

1. A grinding implement for gems and similar hard-faced articles, consisting of a forwardly tapering head with a shank adapted for attaching to a rapidly revolving shaft and provided with a cavity of graduated, stepped cones arranged with a large truncated cone forward.

2. A grindingimplement for gems and similar hard-faced articles, consisting of a forwardly tapering head with a shank adapted for attaching to a rapidly revolving shaft and provided with a cavity of graduated, stepped cones arranged with a large truncated cone forward, the truncated cone having a flat bottom with a dimin- .tial and transvrsal grinding surfaces having rounded edges at their juncture, the surfaces of said cavity forming an outer truncated cone and an inner cone joined by said transverse grinding surface, the base of the inner cone providing a central opening with well-rounded edge in the transverse surface and having its apex adjacent said shank, both cones being coaxial in said REUBEN H. HOOD. 

